A complete sample of bright<i>Swift</i>long gamma-ray bursts: testing the spectral-energy correlations

Abstract

We use a nearly complete sample of gamma-ray bursts (GRBs) detected by the Swift satellite to study the correlations between the spectral peak energy E peak of the prompt emission, the isotropic energetics E iso and the isotropic luminosity L iso . This GRB sample is characterized by a high level of completeness in redshift (90 per cent). This allows us to probe in an unbiased way the issue related to the physical origin of these correlations against selection effects. We find that one burst, GRB 061021, is an outlier to the E peak -E iso correlation. Despite this case, we find strong E peak -E iso and E peak -L iso correlations for the bursts of the complete sample. Their slopes, normalizations and dispersions are consistent with those found with the whole sample of bursts with measured redshift and E peak . This means that the biases present in the total sample commonly used to study these correlations do not affect their properties. Finally, we also find no evolution with redshift of the E peak -E iso and E peak -L iso correlations.